The goal of the PathPhys-Core is to provide state-of-the-art, customized quantitative serum, tissue, and imaging methods to characterize tissue anatomy, damage, and injury in the context of an integrated, biopsychosocial model of cLBP. Additionally, the PathPhys-Core will promote the development and validation of new tools to help identify the molecular, cellular, biochemical, and structural underpinnings of cLBP. The PathPhys Core will consist of three Sub-Cores for Imaging, Tissue Histology, and Serum Analysis. These Sub- Cores will: 1) provide consultation regarding human and sample analyses; 2) standardize protocols; 3) assist with data interpretation; and 4) drive the development of new tools for analyzing pathophysiology and injury. In the context of the overall mission of BACPAC and to support the goals of REACH, the PathPhys-Core proposes the following Specific Aims centered around two themes: innovation and service; education and dissemination. Innovation and Service: Goal is to provide the unique tools for UCSF REACH to characterize tissue anatomy, damage, and injury in the context of cLBP using novel physiology assessment tools. Aim 1: To provide, maintain, and support state-of-the-art quantitative serum, tissue, and imaging methods for pre-clinical and human musculoskeletal tissues. Examples include: MRI pulse sequences for the assessment of endplate structure and permeability (UTE), bone marrow fat content and texture, muscle volume and muscle fat (IDEAL), and disc structure and composition (T2, T1rho). Aim 2: To develop and support novel quantitative serum, tissue, and imaging methods and grading tools. The core will leverage an existing Quantitative Image Processing Center (QUIPC) to provide training, templates as well as software for visualization, post-processing, and quantitative analysis. Examples include: Develop novel image analysis techniques such as texture-based BMF or T1rho distribution, voxel- based morphometry and relaxometry, muscle volume and endplate segmentation algorithms etc. Aim 3: To provide interpretation of imaging data and assess links to the extracted biochemical, histological, and biomechanical measures, and the relevant clinical endpoints. Education and Dissemination: Goal is to disseminate information from the PathPhys Core to the BACPAC consortium, increase research collaborations between sites, and provide educational sessions. Aim 4: To provide web portal access to examples of previous studies that have used serum/tissue/imaging endpoints and detailed descriptions of clinical and research services, and to handle new service requests efficiently through the web portal. Online requests from new users for research collaboration and service will be reviewed by the staff and consultation with appropriate individuals will be set up. Post-processing and imaging informatics will be provided to assist researchers in study design and application. A goal will be to make suggestions as to how best integrate quantitative imaging and analysis into the studies being proposed. Aim 5: To perform proactive outreach to attract potential new users and participate in the BACPAC consortium activities to provide imaging seminars, workshops, and facilities tours that will introduce new imaging and image processing capabilities to the BACPAC community.